The present invention relates to methods and apparatus for testing large-scale integration (LSI).
LSI tests using LSI testers have been conducted in order to select LSIs that operate normally. The LSI testers test target LSIs independently of other components or in combination with simple components that support the test. The simple components are herein passive elements such as relays, resistors, capacitors and filters.
FIG. 10 is a block diagram showing an example of a configuration of a known LSI test system. The LSI test system shown in FIG. 10 includes an LSI tester 2 and a load board 900. The load board 900 includes a socket 14, a relay 82, a capacitor 84, a filter 86, a resistor 88 and a printed circuit board 940.
A target LSI 912 is inserted into the socket 14 and coupled to the LSI tester 2 via the load board 900 so as to be tested. The relay 82 switches the connection between the target LSI 912 and the LSI tester 2. The capacitor 84, filter 86 and resistor 88 are used for changing the characteristics of signals and stabilizing power supply during the test.
The LSI tester 2 tests the actual operation of the target LSI 921 using such a load board 900. Specifically, the LSI tester 2 supplies a predetermined test signal TS0 to the target LSI 912. The target LSI 912 outputs a test result signal TR0 in response to the test signal TS0. Based on the test result signal TR0, the LSI tester 2 determines whether or not the target LSI 912 is defective.
If the target LSI 912 includes an output interface, which operates asynchronously to the main portion of the target LSI 912, and the output interface is to be tested, the output interface is operated independently and is tested.
A technique relating to the present invention is disclosed in Japanese Laid-Open Publication No. 7-128405, for example.
A general LSI tester, however, cannot perform a functional test on a target LSI by simultaneously supplying a given signal and a signal having a frequency which is not an integral multiple of the given signal to the target LSI. Therefore, the load board 900 can easily perform a functional test on a simple LSI in the actual operation but has a difficulty in performing the test on a system LSI (system-on-a-chip) having features of high speed, asynchronous and multiple clocks, in the actual operation. The functional test on a system LSI in the actual operation requires not a general LSI tester but a high-speed and high-performance LSI tester, thus arising a problem of increased cost for the test.
Similar problems are also pointed out in “Major Problems and Solutions of the System LSI Testing” by Tomoyuki Hamasuna in SEMI (semiconductor equipment and materials international) technology symposium 2001 proceedings, pp. 5-81 to 5-88.
Specifically, a test predicated on a SCAN test is effective as a structural test having a purpose of detecting manufacturing defects. However, when the functional circuit structure of the LSI itself becomes complicated, the number of critical paths increases in the actual operation. The SCAN test is not effective for detection of such critical paths.
As well known in the art, a structural test such as the SCAN test and a functional test in the actual operation often have different results of failure detection. The functional test in the actual operation is necessary, but it requires a high-speed and high-functional LSI tester as described above, thus resulting in increased cost for the test.